Photo Color Correction For LTHForum Users [pics]

A Basic Tutelage In Improving Photos After The Fact, Using Whatever Photo Software You Have

One of the things I've been glad to see here is more and more people taking a camera along to document what they eat. Not that anybody wants pictures to replace the thousands of words, but they are a storytelling device in their own right.

Now, one of the things you may have picked up on is a certain debate between GWiv and myself about the use of flash versus natural light. i don't like taking flash photos in restaurants; besides the fact that they attract attention and annoy other people, they don't make either people or food look particularly attractive. I try, as much as possible, to take pictures in natural light, choosing my seat where I might be able to get something like this:



Or this:



Needless to say, it's lunch, not dinner, where you get soft pretty natural white light like that. Alas, at dinner you have to make do with what you have, and often that means an indoor lighting system whose color temperature will make your pictures look like they were taken under bug lamps:



That's a picture of Thai fried chicken that GWiv took, sans flash at my urging, at Silver Spoon a week or so ago. Not an appetizing color, not an accurate depiction of where we ate. But fortunately, there's a good chance that your computer came with some kind of image processing software, and so we can at least improve it somewhat before putting it up on the web.

The most basic tools you are likely to have are controls for Brightness and Contrast. You've probably seen these on a TV, they work very much the same way. First off, this picture is dark, so let's lighten it using the Brightness slider:



The slightly milky look is a result of the slider lightening it across the board. We'll use Contrast to restore the punch that Brightness took out:



That's somewhat better, but it still hasn't gotten rid of that jaundiced cast the picture has. For that you need a subtler set of tools: Curves.

Curves give you control over every level of the image, from the lightest to the darkest areas, and what's more, they give you control over each of the three primary additive colors-- red, green and blue-- individually.

Let's start by lightening all three colors at once (note the menu says "RGB"). But where the Brightness slider would raise everything equally, we're going to raise the light end of the spectrum, so that the white tablecloth gets the most effect, the glass of wine gets somewhat less, and the darker parts of the chicken get little to none:



Notice that I added a point to the middle of the spectrum and nudged it just a hair higher. I can't tell you why I did that, precisely, but it just seemed like the middle needed a little more. Anyway, next we go into the Green curve and lower it as far as we can to get rid of that yellow cast:



The tablecloth has a distinct rosy cast now, so we're going to try to simulate white light by upping the Blue, much as your grandma added Household Bluing to her wash to counteract the yellowing of cotton:



The colors are more natural now in general, but they're still dark. So we go back to the RGB curve and fiddle with some different points of the spectrum until we get something that's lighter, not too rosy, etc.:



This is where the art really comes in, but with practice you too will sense instinctively which ways to push an image to get something that is, if not a great photo, at least a decent one that bears an acceptable resemblance to the meal we actually ate:



Here's the original again so you can compare:

Mike G wrote:I try, as much as possible, to take pictures in natural light,

Mike,

I agree 100% natural light is best. Where I disagree is on the use of the flash indoors in an evening restaurant setting. I simply do not find the majority of non-flash food pictures taken at night in restaurants visually appealing.

For example, this flash picture of Silver Spoon's Thai Fried Chicken was taken, literally, seconds after the non-flash picture you are working with. I prefer the flash picture to the non-flash.



Admittedly, many of the flash pictures I take do not come out well, and there may be a small annoyance factor to other diners, but overall if there is not adequate natural light I prefer using the flash.

Thank you for the color correction tutorial. Hopefully that and a greater understanding of the various photographic options will enhance my picture taking and posting ability.

Enjoy,
Gary

Mike,

Great tutorial, but I would also add that using curves to color correct pictures is akin to cooking a brisket on a WSM. You have to take several steps before you get to the point where you are competant to do it. Using the "levels" adjustments is an easier way (for beginners) to achieve much the same results. Maybe even better.

Before


After

Hi Mike,

Thank you for this tutorial.

I have been creating and editing images for the Pie History talk. I can crop, enlarge and edit pictures until the cows come home. I have been having problems getting the right hue. Same scene taken by the same camera can be just right, grey-ish, orange-ish or flash-light bright --- all taken seconds apart. Unfortunately, just-right seems to be least likely result. Your tutorial will be my guide to correcting those images further.

Thank you.

Regards,

Ah, but Steve, the nice thing is, it's a brisket with a reset button. That's why I think it's well worth anyone taking a little time to play with curves and learn how they work-- you can always throw the result away and have exactly the picture you started with.

To Gary's point, in this case you're probably right, the slight glare of the flash on the chicken is probably compensated for, at least on an accuracy basis, by the fact that this is pretty much dead on for color. But the real issue is what you're taking the pictures for, your own aesthetic standards, etc. Some might like to document everything, and if that requires something that's just okay as a photo, that's okay. Me, I'm not inspired to put up a photo essay unless I actually have pictures I like. I'd rather not take pictures than take them under conditions that don't appeal to me. So knowing some color correction helps me move a few more shots over to that column. Of course, in dubious circumstances, one should always snap the same shot with and without flash, to be safe.

And with that-- let a thousand photos bloom!

Mike,

Please don't get me wrong. Color correction is something that is important to know about. A well corrected shot can salvage an otherwise unusable picture. I just think that levels is an easier tool to use than curves. Both can achieve the same result, it's just that one is easier to use than the other. I'll put together a tutorial similer to yours using levels if I get a chance.

As promised, here is a tutorial for color correcting your pictures using the levels control. I did this using Photoshop, but levels should be present in almost any image editing software. In Photoshop, you can access the level adjustments under Image>Adjustments>Levels. Please note that there is a selection labeled "Auto Levels". If your picture is close to perfect, this selection may work for you. It's worth a try. If you don't like the results you get using "Auto Levels", hit the undo button and select "Levels". This is meant to be an alternative method to Mike's excellent tutorial about using curves. I think this might be a superior method to use for this task because you don't have to pick an arbetrary point on the curves adjustment to correct your picture. That is an advanced technique that can be used in conjunction with this one for fine tuning your color, but for quick color correction, here's what to do:

Start:


As you can see from the levels histogram, all of the information in this image is to the left, or dark, part of the range. Your goal is to spread the information out over the entire range of histogram.

Step 1:


Use the drop down menu at the top of the histogram to select the red channel. Slide the right hand arrow at the bottom of the histogram to the left until it is under the farthest right side of the displayed histogram information. Click OK.

NOTE: This technique works equally well for blown out shots where the histogram is moved to the right side of the range. Just use the left arrow instead of the right arrow for those types of corrections. The only caveat for that type of color correction is that you cannot replace detail in the picture due to blown out highlights (bright spots). That data is simply not saved in the file.

Step 2:


Repeat for the green channel. Notice how green the image looks now. Don't panic, you still have blue to go.

Step 3:


Look. After you adjust the blue channel, the image has magically been corrected for both brightness and white balance. Click OK. It looks pretty good and it's hard to believe that this is the image you started off with. But wait; doesn't that chicken and dipping sauce look a little lackluster and in the shadows? We want that to pop out a little more.

Step 4:


Here's where Mikes "Curves" adjustments would come in real handy, but there is one more trick in the levels pallette that can save the day. Notice on the histogram that you have now spread the image information all the way across the range of the histogram. Select the red channel again.

Step 5:


To my eye, it looked like the red channel needs to pop a little more, but I don't want to change the color balance, which is just right. Move the center arrow at the bottom of the histogram slightly to the left. It doesn't take much (note the center value box changed from 1.0 to 1.21. That's all the change needed to change the gamma (or contrast) of the red channel to make it pop that chicken and dipping sauce out more.

That's it. Hopefully this will help you fix those dark, bad color balance natural light photos.

Or you could purchase a tungsten filter and put that over the lens before you take the picture, and be done with it. This light blue filter always worked for me to adjust daylight film color balance to indoor lighting (incandescent bulbs, that is). At least that's what I used to do in the days of "film" photography. Looking at the "before" and "after" pics from your Photoshop adjustment sessions, I see little difference between a Kodacolor outdoor print film shot without a tungsten filter (your "before" shot) and with the filter (your "after" shot). Of course, diddling the knobs can be half the fun (Photoshop is like a surrogate for a projector and a sink full of trays, and doesn't require light-proofing your basement) so I understand the appeal.

JimInLoganSquare wrote:Or you could purchase a tungsten filter and put that over the lens before you take the picture, and be done with it. This light blue filter always worked for me to adjust daylight film color balance to indoor lighting (incandescent bulbs, that is). At least that's what I used to do in the days of "film" photography. Looking at the "before" and "after" pics from your Photoshop adjustment sessions, I see little difference between a Kodacolor outdoor print film shot without a tungsten filter (your "before" shot) and with the filter (your "after" shot). Of course, diddling the knobs can be half the fun (Photoshop is like a surrogate for a projector and a sink full of trays, and doesn't require light-proofing your basement) so I understand the appeal.

Unfortunately, it's not practical to use filters with small digital cameras. They don't make them for the tiny lenses of pocket sized models, so this is how you have to manage color for shots taken in existing light without a flash, which is what both Mike G and I are advocating.

Steve -- I figured from the deeply technical discussion here that you were using a professional model digital camera, not a compact -- mea culpa!

JimInLoganSquare wrote:Steve -- I figured from the deeply technical discussion here that you were using a professional model digital camera, not a compact -- mea culpa!

I have found that the secret to success in chow photography is to always have a camera in your pocket at the ready. As much as I would like to use a good digital SLR for these shots, it's just not practical to always carry one around.

The Olympus Stylus 410 may be the camera you need. Read the following from a story in today's Tribune:

"Of the eight scene modes on the new Olympus Stylus 410 digital camera, the cuisine option is the most intriguing. It helps the photographer take better pictures of food by increasing the saturation, sharpness and contrast settings.

Some diners are so impressed by the presentation of an entree that they want to photograph their plate, but will they actually go to the trouble of setting their camera to cuisine mode? Probably not."

Or in your case, most definitely so!